This invention relates to the field of liquid sample analysis; more particularly, the present invention addresses the problems of monitoring the properties of liquids in inaccessible areas.
When monitoring liquid flows for indications of contamination, it is frequently necessary to get as close as possible to the source of contamination to maximize the probability for accurately detecting the contamination. Getting as close as possible to a source of contamination leads to physical accessibility issues, which can best be mitigated by making only two visitsxe2x80x94one visit to leave a liquid sample monitoring system in place and one visit to retrieve it. Prior art liquid flow monitoring systems have suffered from either the inability to pinpoint when the contamination occurred or the inability to monitor continuously for extended periods of time.
Electromechanical liquid monitoring devices are not new in the prior art. Typically, prior art electromechanical liquid monitoring devices have been designed for a limited use and include features specifically directed to the specific liquid being measured and the degree of measurement accuracy required.
Exemplary of prior art electromechanical liquid monitoring devices are the following:
U.S. Pat. No. 4,039,933 describes an instrument for blood chemistry analysis. Key to the operation of the disclosed instrument are the automatic calibration electronics. Not included in the disclosed invention are any provisions for liquid flow control or storage of the liquid samples analyzed by the instrument.
U.S. Pat. No. 4,478,222 describes an instrument that utilizes a reference liquid flow passage in its body portion. Electromechanical sensors, such as ISFET (ion selective field effect transistor) devices are used for sensing the presence of a particular ion in the analyzed liquid. U.S. Pat. No. 5,405,510 describes a portable liquid analysis system. U.S. Pat. No. 5,976,085 describes a liquid analysis system that uses electrical control of on-board valves to alter the flow of blood through the analysis system. The Monterey Bay Aquarium Research Institute (MBARI) developed a device called the Osmo Sampler, which was first described in 1991 at an IEEE (Institute for Electronic and Electrical Engineers) meeting. In the Osmo Sampler, a sample of sea water was reacted with chemical reagents while it was contained inside a capillary. Color changes were detected in situ. The color changes were used to identify the presence of nitrate ions in the sampled sea water. The Osmo Sampler used osmosis to drive the sea water through the system and perform a continuous analysis. Later versions of the Osmo Sampler were designed for deployment and retrieval after unattended operation.
The present invention describes an unattended, self calibrating, microprocessor controlled, electromechanical liquid sample monitoring and liquid sample storage system.
The disclosed liquid sample monitoring and liquid sample storage system is designed to facilitate remote liquid quality monitoring by being both portable and capable of many months of unattended operation. Specifically, the disclosed system includes a filtered inlet, a microfluidic manifold having a pressurized reference liquid injector system and sensors for the measurement of various liquid parameters, one or more parallel long glass capillaries and a microprocessor assembly with analog-to-digital converters and a non-volatile memory. The entire liquid sample monitoring and liquid sample storage system is enclosed in an evacuated housing.
At the end of the desired liquid monitoring period, the system is retrieved and the critical sensor measurements are uploaded from the onboard microprocessor. Additional information about the properties of the liquid sampled may be obtained by breaking the capillary open and subjecting the liquid samples stored within the capillary to a full laboratory analysis. The capillary is physically filled with the liquid being sampled by slow suction into a pre-evacuated volume, thus eliminating the power requirements and complexity of a mechanical pump for drawing the liquid to be analyzed into the system.
The design of the system facilitates long-term unattended operation. The properties of liquids may be monitored continuously such that the presence of rare and/or brief transient contaminants in the liquid flow are not missed.